Fittings for controlling flow through drain openings typically have a closure member which seats against the inlet end of the opening either directly or through an annular resilient sealing element. The closure member is coupled to other components through mechanism for shifting the closure member outward from the drain opening when fluid is to be drained through the fitting.
Such mechanism in a number of prior drain fittings of this kind includes a spring or an elastomeric sleeve which acts to urge the closure member away from the closed or seated position. Such fittings are closed by manually forcing the closure member to the seated position against the force of the spring. Detents or other latching means then engage to resist the spring force so that the closure member may remain at the seated position. Prior mechanisms of this kind resist movement of the closure member away from the seated position but do not apply any significant positive sealing pressure to the closure member when it is at that position.
Prior drain fittings of this type rely on a combination of gravity and the pressure of overlying liquid to apply sealing force to the closure member. These forces are not always as effective for the purpose as would be desirable. Drain fitting components are usually not particularly massive and thus the gravitationally generated force is limited. Fluid pressure is dependent on the height of the liquid above the drain closure and there is frequently only a minimal volume of such liquid present, particularly during initial filling of a bathtub, wash basin, kitchen sink or the like and occasionally at other times as well. Turbulence and the motions of persons using the installation can also cause some slight unseating of the closure member. Insufficient sealing force also detracts from the effectiveness of elastomeric seals where these are present in drain fittings.
Consequently, some leakage of liquid through drain fittings has been a common occurrence. While this is usually tolerable and generally accepted, it would be preferable to avoid or minimize such leakage for a number of reasons. Replenishing the liquid in a bathtub or sink during use can be a significant inconvenience. Efforts are being made in many regions to conserve limited water supplies and leakage of the above discussed kind is counterproductive to such programs. Additives such as soap, detergents or medications, for example, are often present in sinks or bathtubs and leaking drain fittings cause a wastage of such materials.
The present invention is directed to overcoming one or more of the problems discussed above.